Preface to the Third Edition

Much of the justification for the second edition applies to this third edition as well, but more so (as it were). Again the book has benefited from experience gained in teaching the material in various live classes. There are revisions of substance to many of the chapters, based on any or all of the following: changes to the SQL standard, improvements to Tutorial D, improvements in my own understanding of relational theory, better ways of presenting some of the material, and (in a few cases) simple corrections of errors. Also, in response to requests from readers:

• I’ve increased the font size. (My own eyesight isn’t what it used to be, either.)

• I’ve replaced all “smart quotes” in coding examples by “dumb quotes,” in order to help with cut and paste operations.

• I’ve moved exercise answers to the chapter in which they belong (and set them in a different typeface), instead of putting them all in an appendix of their own at the back of the book.

I’ve also added an appendix on the new “NoSQL” systems, in which (as the title of that appendix indicates) I’ve tried to show what the relationship is between those systems and relational theory. Finally, textual and formatting improvements have been made throughout.

C. J. Date
Healdsburg, California
2015